The present invention relates to a method and system for preventing unwanted rolling away of a vehicle, and more particularly, to a method in which rolling away is prevented by maintaining a brake pressure in wheel brake cylinders, and the brake pressure maintained being dependent on the actuation of the brake pedal, the speed of the vehicle being determined.
DE 29 11 372 discloses a brake system which has a rotational-speed detection system which is linked to the direction of rotation and actuates the brakes if the vehicle starts to roll in the opposite direction to the direction of the gear selected, i.e. rolling backwards when a forward gear has been selected and vice versa. When the brake system is deactivated, the pressure dissipation takes place as a function, inter alia, of the engine speed. Owing to the system configuration, triggering the brake actuation requires an engaged gear. No brake actuation takes place at idle. Moreover, the driver has no influence on the triggering of brake actuation.
DE 031 13 362 discloses that the ignition and the brakes can be coupled to ensure that the brakes are automatically actuated when the vehicle is parked.
An object on which the invention is based is to provide a system which prevents a stationary vehicle from unintended movement and which can be activated at will by the driver.
According to the present invention, this object has been achieved by providing that a variable which represents the actuating force applied by the driver is detected, a first value of the variable being determined in a first time interval following the onset of the stationary condition of the vehicle and, when the current value of the variable exceeds a second value of the variable, which is higher by a predetermined amount than the first value, at least the brake pressure which corresponds to an actuation of the brake pedal with the first value of the variable is maintained irrespective of a subsequent release of the brake pedal.
The system of the present invention has the advantage that, when the vehicle is stationary, brakes are actuated only if the brake pedal has been actuated. The brake system is triggered by the driver by an additional actuation of the brake pedal. This has the advantage, as compared with the conventional approach, that the system can be controlled at will by the driver.
A further advantage of the present invention is that components of the existing ABS can be used. The system furthermore remains activated when the idling speed has been selected to facilitate, among other things, parking.
According to another embodiment of the invention, a signal from the ignition is detected and, if the engine stalls but the ignition is still switched on, braking force is maintained to ensure that the vehicle does not roll away. Moreover, the brake pressure does not necessarily have to be dissipated when the ignition is off because, otherwise, the vehicle would roll away when the driver restarted the vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.